Air conditioning systems are currently commonplace in homes, office buildings and a variety of vehicles including, for example, automobiles. Over time, the refrigerant included in these systems becomes depleted and/or contaminated. As such, in order to maintain the overall efficiency and efficacy of an air conditioning system, the refrigerant included therein is periodically replaced or recharged.
Portable carts, also known as recover, recycle, recharge (“RRR”) refrigerant service carts or air conditioning service (“ACS”) units, are used in connection with servicing refrigeration circuits, such as the air conditioning unit of a vehicle. The portable machines include hoses coupled to the refrigeration circuit to be serviced. A vacuum pump and compressor operate to recover refrigerant from the vehicle's air conditioning unit, flush the refrigerant, and subsequently store the recovered refrigerant in a refrigerant storage tank, also referred to as an internal storage vessel or ISV. The refrigerant can then be used in another refrigeration system.
A typical ACS unit is further configured to charge the refrigeration circuit with a specified quantity of refrigerant from the ISV after the recovery operation is complete. During a charge operation, a valve between the ISV and the refrigeration circuit is opened, connecting the refrigeration circuit to the ISV. The refrigerant is stored in the ISV at the saturation pressure of the refrigerant at the temperature of the refrigerant in the ISV. The pressure differential between the ISV and the empty refrigeration circuit results in the refrigerant moving from the ISV into the refrigeration circuit.
In some instances, however, the pressure in the refrigeration circuit may equalize with the pressure in the ISV prior to the charge being completed. Since the charge relies solely on the pressure differential to transfer the refrigerant from the ISV to the refrigeration circuit, the charge stalls and no more refrigerant flows into the refrigeration circuit.
In some systems, the ACS unit performs a “power charge/recycle” operation to finish a charge after the charge has stalled. The refrigerant is cycled through a recovery path and the compressor, and moves back to the ISV. The compressor heats the refrigerant as it passes through, increasing the saturation temperature of the refrigerant and therefore enabling the refrigerant to flow from the ISV to the refrigeration circuit again. Performing a power charge/recycle operation, however, is time consuming and results in a substantial increase in the duration of the charging operation.
What is needed, therefore, is an ACS unit that can reduce the likelihood of a stalled charge condition and that can recover quickly from a stalled charge condition.